Lindsey Graham's Cause of Death Revealed by Spokesperson

Lindsey Graham's died from a tear in his aorta ... this according to his longtime spokesperson.

Taylor Reidy -- Graham's communications director -- shared the news to X just moments ago ... writing the information comes from the Medical Examiner of the District of Columbia’s preliminary findings.

According to the preliminary exam, Graham died from "aortic dissection due to arteriosclerotic cardiovascular disease."

The Mayo Clinic states an aortic dissection is a tear in the inner layer of the aorta, the body's main artery. Blood rushes through the tear and, if the blood goes outside the artery, it is often deadly.

In this case, the M.E. indicates the dissection was caused by the hardening and narrowing of arteries due to plaque buildup.

It's worth noting -- as Reidy does -- that these are not the final autopsy results ... and things could change in the course of investigation.

As you know ... Graham's team released a statement late Saturday night announcing his passing from a "brief and sudden illness."

We obtained photos from outside Graham's home ... which show the senator being wheeled out on a gurney. 911 audio indicated he'd been suffering from chest pains before the call was made.

President Donald Trump and multiple other world leaders have paid tribute to Graham in the aftermath of his passing ... and flags are now being flown half-staff in his honor.

Graham was 71.